Carbon emissions make satellites move faster

It's a non-intuitive consequence of CO2 emissions and climate change.

When you think about CO2 emissions from the use of fossil fuels, you probably think about climate change. Temperature. Maybe precipitation patterns. Storms. But do you think about managing the orbital mechanics of satellites?

As humans, we really only experience the lower atmosphere—the troposphere and stratosphere that extend about 30 miles from the surface. That’s where nearly all of the gas in the atmosphere resides, and that’s where weather happens. Even Felix Baumgartner, the daredevil skydiver, "only" jumped from the stratosphere. But technically, the atmosphere extends a whole lot higher than that. It’s another 150 miles or so before we truly reach interplanetary space. A number of satellites, as well as the International Space Station, are actually whizzing around in a layer of the atmosphere called the thermosphere.

Down in the troposphere, CO2 is an important greenhouse gas. Add more CO2, and you trap more outgoing heat, warming the lower atmosphere. But up in the thermosphere, things are much different. Gas molecules are incredibly sparse—and increasingly so as you head outward from the Earth. Here, CO2 is actually a key coolant, as it absorbs energy from collisions with oxygen molecules, and then emits that energy as infrared radiation, sending much of it out into space.

And when the thermosphere cools, it contracts. That results in fewer molecules in the orbital paths of satellites, meaning the drag slowing their motion decreases. This phenomenon made news in 2010, when the thermosphere contracted to its smallest extent in 40 years of record. That was caused by low solar activity, but researchers noted that this didn’t fully explain the low point, suggesting that rising CO2 concentrations may have been involved in the long-term trend.

One of those researchers (along with several of his colleagues) has now published the results of an analysis of CO2 in the thermosphere. It’s a difficult thing to measure, but they used data the Canadian SCISAT-1 satellite collected by observing the setting Sun through the thermosphere above the horizon from 2004 to 2012. To untangle trends from variability caused by solar activity, they combined measurements of carbon monoxide and carbon dioxide. Ultraviolet light splits a portion of the CO2 into CO, which can be oxidized to turn back into CO2.

Added together, the trend becomes clear—CO2 in the thermosphere increased at a rate of 23.5 ± 6.3 parts per million each decade. That’s much more than was previously thought, and it appears to account for the trend toward contraction of the thermosphere.

The researchers say that this unexpectedly large increase indicates that more mixing takes place between the thermosphere and the lower atmosphere (where anthropogenic CO2 is accumulating) than we realized. When they increased that vertical mixing in an atmospheric climate model, the behavior of the thermosphere matched the new observations.

This story illustrates some of the non-intuitive consequences of CO2 emissions and climate change. While politicians continue to debate the reality of climate change, the professionals who manage satellites show up to work and get down to the practical details of dealing with that reality. In this case, that means accounting for fine-scale modifications to the motion of satellites and space debris caused by a changing climate system. That will require continued monitoring of thermospheric CO2 to see if the upward trend observed over the past eight years continues smoothly or is altered by vertical mixing behavior or other processes.

66 Reader Comments

wait, is it larger concentrations of CO2 causing the satellites to speed up? or is the the warming of the earth that's causing it?

Is warming of the earth causing an increase in the concentration of of CO2 which then causes the satellites to move faster, or is the human-caused increase of CO2 concentration responsible for both lower atmo. warming, and upper atmo cooling?

Wow, this is interesting, and as noted, totally unexpected given previous models of mixing between atmospheric layers. Increasing CO2 buildup isn't good, but it sure is teaching us new things about how this planet operates.

Because of drag, orbits decay and require periodic correction to prevent the satellite (or space station) from shifting orbits or de-orbiting. A decreased drag force would make these corrections less frequent, which, unlike global warming, may actually be a good thing.

Because of drag, orbits decay and require periodic correction to prevent the satellite (or space station) from shifting orbits or de-orbiting. A decreased drag force would make these corrections less frequent, which, unlike global warming, may actually be a good thing.

wait, is it larger concentrations of CO2 causing the satellites to speed up? or is the the warming of the earth that's causing it?

Is warming of the earth causing an increase in the concentration of of CO2 which then causes the satellites to move faster, or is the human-caused increase of CO2 concentration responsible for both lower atmo. warming, and upper atmo cooling?

Because of drag, orbits decay and require periodic correction to prevent the satellite (or space station) from shifting orbits or de-orbiting. A decreased drag force would make these corrections less frequent, which, unlike global warming, may actually be a good thing.

Actually, you could argue that an orbit is essentially a constant state of falling (as gravity continues to pull satellites towards earth). The change in drag would allow them to "fall" faster.

A decrease in drag wouldn't cause satellites to speed up; that would violate the basic laws of physics.

I think the headline is meant to be read as "Warming Earth makes satellites move faster [than they would otherwise]", as in comparison to a steady-state Earth. There was really no wording in the article to suggest a net increase in orbital velocity. I think it was explained carefully enough.

pancakesandbeyond wrote:

wait, is it larger concentrations of CO2 causing the satellites to speed up? or is the the warming of the earth that's causing it?

To expand/clarify what bartfat said: The satellites travel through the thermosphere. CO2 cools that particular layer, causing it to "shrink" (thin out). Therefore there are fewer atmospheric molecules in the path of the satellite (less frictional drag).

So a measurement of a satellite's speed will show it going faster than would have been expected with no net CO2 accumulation.

Because of drag, orbits decay and require periodic correction to prevent the satellite (or space station) from shifting orbits or de-orbiting. A decreased drag force would make these corrections less frequent, which, unlike global warming, may actually be a good thing.

This ^^^ Glad I read the quotes before popping off. I read the headline alone and thought "This cannot be right". You would need to apply a force to the satellite to increase it's velocity. The lower coefficient of drag will reduce the rate in which the satellite's orbit degrades, not make it move faster.

I'm not bashing AGW. I am a believer. I am merely pointing out that CO2 emissions from any source will accumulate in the atmosphere...not just the anthropogenic stuff. When I said "by what process is this distinction being made", I meant, "by what natural process is the non-ACO2 being separated from the ACO2".

Because of drag, orbits decay and require periodic correction to prevent the satellite (or space station) from shifting orbits or de-orbiting. A decreased drag force would make these corrections less frequent, which, unlike global warming, may actually be a good thing.

THIS.

Less atmospheric drag means less orbital decay. As a result satellites need orbital corrections less often (posigrade burn), or they can stay in low orbit longer without said orbital corrections before they deorbit.

Nothing is going to make a satellite go faster without some sort of a thruster fire or engine burn.

This phenomenon will save money and maybe prolong the life expectancy of some satellites. It won't make them orbit any faster.

I'm not bashing AGW. I am a believer. I am merely pointing out that CO2 emissions from any source will accumulate in the atmosphere...not just the anthropogenic stuff. When I said "by what process is this distinction being made", I meant, "by what natural process is the non-ACO2 being separated from the ACO2".

However, I suppose there might be isotopic stratification?

Actually the "accumulation" would be more like steady-state replacement, or even decrease, without anthropogenic contributions. Atmospheric CO2 concentrations are rising at half the rate of anthropogenic CO2 emissions. That means on average we're emitting twice as much CO2 as the total increase every year. That the rise is slower than the emissions tells me that without the anthropogenic emisssions, there wouldn't be growth; there wouldn't be "accumulation." This is backed up by the relatively stable amount of CO2 in the atmosphere for thousands of years prior to the industrial revolution.

Orbital mechanics are somewhat non-intuitive. When a spacecraft fires it's retro-rockets, they cause it to drop into a lower orbit (or out of orbit). But lower orbits have a higher orbital velocity (Earth orbits the sun in 365 days, mercury in a lower solar orbit takes 88 days to circle the sun). More friction would result in the satellite dropping into a lower orbit, where it's orbital velocity is greater. Less friction would allow the satellite to stay in the same orbit longer, but it would not, as you say, go any faster. Rather it would stay slower longer. I don't think the title is right in this case.

Quote:

Because of drag, orbits decay and require periodic correction to prevent the satellite (or space station) from shifting orbits or de-orbiting. A decreased drag force would make these corrections less frequent, which, unlike global warming, may actually be a good thing.

The spin on why it was bad in 2010 was because it would allow space junk to stay in orbit longer and be a danger to the shuttle/ISS/satellites.

If there is more interatmospheric mixing of CO2 than we previously thought, does this mean that we need to revise our estimates about how much CO2 escapes the earth's atmosphere?

Would this decrease the average time aloft of a CO2 molecule in our atmosphere and decrease the steady-state CO2 asymptote of atmospheric concentrations?

In contrast to that thought, if the increased CO2 concentrations in the thermosphere are cooling(and thus shrinking) it, would this mean that the average time aloft of gas molecules in the upper atmosphere would decrease because less of them would be traveling faster than escape velocity? Gases with low atomic weights have very large standard deviations in average molecular velocity.

One other thought: for those of us thinking about the thermosphere as creating "drag," it's not actually fluid dynamics. The modeling to calculate the "drag" on satellites in low earth orbit is actually done by calculating the effects of each individual particle impacting the satellite. There are not enough particles to form a boundary layer. Thus, thinking of them as "gases" is really quite a stretch.

I'm not bashing AGW. I am a believer. I am merely pointing out that CO2 emissions from any source will accumulate in the atmosphere...not just the anthropogenic stuff. When I said "by what process is this distinction being made", I meant, "by what natural process is the non-ACO2 being separated from the ACO2".

...More friction would result in the satellite dropping into a lower orbit, where it's orbital velocity is greater. Less friction would allow the satellite to stay in the same orbit longer, but it would not, as you say, go any faster. Rather it would stay slower longer. I don't think the title is right in this case.

Well, yes, but you're entering an orbit that would have required less Delta-V to achieve, and thus "decelerating". Instantaneous velocity is decreasing. I totally agree orbital mechanics are non-intuitive and I think we're on the same page.

AnonymousRich wrote:

The spin on why it was bad in 2010 was because it would allow space junk to stay in orbit longer and be a danger to the shuttle/ISS/satellites.

I suppose that's plausible, but certainly wouldn't be my first thought.

It seems like "Warming Earth makes satellites move faster than expected" is the intended meaning of the headline, but it was abbreviated for whatever aesthetic informs headline-writing. This is why I never assume a headline is saying exactly what the article is saying, outside of The Onion where the headline is all you need to read.

...More friction would result in the satellite dropping into a lower orbit, where it's orbital velocity is greater. Less friction would allow the satellite to stay in the same orbit longer, but it would not, as you say, go any faster. Rather it would stay slower longer. I don't think the title is right in this case.

Well, yes, but you're entering an orbit that would have required less Delta-V to achieve, and thus "decelerating". Instantaneous velocity is decreasing.

Agreed, next comes the lower (or de-) orbit at a higher velocity.

Quote:

I totally agree orbital mechanics are non-intuitive and I think we're on the same page.

Agreed again.

Quote:

AnonymousRich wrote:

The spin on why it was bad in 2010 was because it would allow space junk to stay in orbit longer and be a danger to the shuttle/ISS/satellites.

I suppose that's plausible, but certainly wouldn't be my first thought.

Yes, my first thought was that satellites and the ISS and stuff in LEO would stay in orbit longer. But I suspect that the difference is negligible.

I'm not bashing AGW. I am a believer. I am merely pointing out that CO2 emissions from any source will accumulate in the atmosphere...not just the anthropogenic stuff. When I said "by what process is this distinction being made", I meant, "by what natural process is the non-ACO2 being separated from the ACO2".

However, I suppose there might be isotopic stratification?

Actually the "accumulation" would be more like steady-state replacement, or even decrease, without anthropogenic contributions. Atmospheric CO2 concentrations are rising at half the rate of anthropogenic CO2 emissions. That means on average we're emitting twice as much CO2 as the total increase every year. That the rise is slower than the emissions tells me that without the anthropogenic emisssions, there wouldn't be growth; there wouldn't be "accumulation." This is backed up by the relatively stable amount of CO2 in the atmosphere for thousands of years prior to the industrial revolution.

OK...I have now written about 5 versions of this post which reflect various stages of the continuing education of DoomHamster. I am forced to concede both a pedantry and snark failure.

The key as Scott says is the term accumulating. The non-ACO2 isotopes appear to be dropping off so they by definition cannot be accumulating even if non-ACO2 from new sources is arriving in the atmosphere and thermosphere, whereas the ACO2 isotopes are, indeed, accumulating.

So thanks, Scott and WoC for clarifying even though it should not have been necessary.

How much of the added CO2 in the thermosphere is directly from rocket exhaust?

My estimate: none. According to Wikipedia, except for the first stage of some rockets there is no carbon in rocket fuel. Since the first stage burns out long before the rocket gets to the thermosphere, there is no reason to expect that any CO2 is created in this region.

How much of the added CO2 in the thermosphere is directly from rocket exhaust?

Actually that's an interesting question. I would think that a rocket launch would emit exhaust gas directly into the thermosphere.

But the main thrusters of the shuttle burn LOX and liquid hydrogen so I don't think there would be any thermospheric CO2 exhaust from shuttle launches. This assumes that the solid rocket boosters drop off well before the thermosphere is reached. I think spaceX uses LOX/kerosene so CO2 it would probably put a fair amount of CO2 into the thermosphere. But how this compares to normal diffusion I have no idea.

How much of the added CO2 in the thermosphere is directly from rocket exhaust?

Actually that's an interesting question. I would think that a rocket launch would emit exhaust gas directly into the thermosphere.

But the main thrusters of the shuttle burn LOX and liquid hydrogen so I don't think there would be any thermospheric CO2 exhaust from shuttle launches. This assumes that the solid rocket boosters drop off well before the thermosphere is reached. I think spaceX uses LOX/kerosene so CO2 it would probably put a fair amount of CO2 into the thermosphere. But how this compares to normal diffusion I have no idea.

Damn. I was looking for neil5280's answer for about an hour. I was fairly certain I saw a figure somewhere, Just looked again after an after hour adult beverage. Thank you Cliff Clavin.

Quote:

This increase is 10 parts per million per decade faster than predicted by models of the upper atmosphere. Launching rockets into orbit does add carbon dioxide to the atmosphere, but the scientists calculated that such launches would have deposited only about 2,700 metric tons of carbon into the upper atmosphere between 2004 and 2012, while levels of COx apparently rose by about 20,000 metric tons in the upper atmosphere during that time.

Do you have a point to make about the quality of measurements made using the SCI-SAT1 for this study? Or are you just here to stick your head in the sand and guffaw, as usual?

Yes the quality of measurements and the quality of this study are prime suspects here. How else some trace gas together with dubious stratosphere temp increase can cause anything but footnote at fifth decimal place?

How much of the added CO2 in the thermosphere is directly from rocket exhaust?

Actually that's an interesting question. I would think that a rocket launch would emit exhaust gas directly into the thermosphere.

But the main thrusters of the shuttle burn LOX and liquid hydrogen so I don't think there would be any thermospheric CO2 exhaust from shuttle launches. This assumes that the solid rocket boosters drop off well before the thermosphere is reached. I think spaceX uses LOX/kerosene so CO2 it would probably put a fair amount of CO2 into the thermosphere. But how this compares to normal diffusion I have no idea.

As noted above, there probably isn't any CO2 emitted directly into the thermosphere, although the ascent of the rocket itself might do a bit of unnatural vertical mixing. Returning spacecraft might create a smallish splash in the stratosphere, too, but my guess is that would be the smaller of the two effects.

Edit: returning spacecraft would be just like meteors, which are nothing new for the Earth system. Shooting stuff out is a fairly recent development, geologically speaking.

Do you have a point to make about the quality of measurements made using the SCI-SAT1 for this study? Or are you just here to stick your head in the sand and guffaw, as usual?

Yes the quality of measurements and the quality of this study are prime suspects here. How else some trace gas together with dubious stratosphere temp increase can cause anything but footnote at fifth decimal place?

Yes, reality really is a pain in the ass sometimes, isn't it? It's a damn shame that 2+2 does not equal cupcakes.

How else some trace alcohol in your blood can cause anything but footnote at fifth decimal place of driving skills?